1. Field of the Invention
The present invention relates generally to commercial and architectural windows and, more particularly, to an integrated multipane window unit and sash assembly and a method for manufacturing the same.
2. Description of the Related Art
As is currently well-known in the art, insulating glass units, or IG units, are currently widely used as elements of windows and doors. Such units are used in windows and doors to reduce heat loss from building interiors in winter, and reduce heat gain into air-conditioned buildings in summer. The insulating glass units are typically formed separate from the sash, and then in a separate step the insulating glass unit is installed in a sash.
IG units generally consist of two parallel sheets of glass which are spaced apart from each other and which have the space between the panes sealed along the peripheries of the panes to enclose an air space between them. Spacer bars are placed along the periphery of the space between the two panes. The spacers are assembled into generally rectangular-shaped frames either by bending or by the use of corner keys.
As has evolved in the present commercially successful technology, insulating glass units form only the internal components of a sash element used in a window unit. A sash element forms the working element of the window, and forms a perimeter called a sash frame that holds necessary working hardware to allow the sash element to slide, locks, crank, et cetera.
Although many materials of construction are conventionally utilized for manufacturing of sash elements, such as wood and aluminum, presently available insulating window units that utilize a sash element formed of extruded polyvinyl chloride polymers are known to provide a superior insulating effect in conventional commercial and residential applications.
In the manufacture of conventional sash, one starts with extrusion called a "PVC" profile. These extrusions can be purchased from an extrusion manufacturer designed to make a style having a certain aesthetic. Extrusions can be made generally available to the marketplace; however, a general practice that has developed is to provide a partial exclusivity by region, market, etc. in order to allow a particular window manufacturer to associate a certain aesthetic with that manufacturer's product. Therefore, although many extrusion profiles are of an original design, they are treated in the marketplace as a quasi-commodity.
Another aspect of the extrusion profile is that given that the exterior surface must mate with the main frame, the profile is also functional as well as aesthetic. In order to accomplish this functionality, changes are made in internal grooves, channels, etc.
The next element in the manufacture of a sash is to cut corner miters in the sash element. These cuts are made in an oversized manner, by 1/4 to 1/8 inch. This additional material is to allow for a process called vinyl welding, in which both seams are heated to a point wherein the PVC material softens and the joint is pressed together and cooled in place to form a cohesive bond. This process forms a corner joint that is stronger than the original extrusion.
The manufacture of the sash results in a four-sided sash frame. However, a flash buildup or `swath` is formed by the vinyl welding process, which must be milled, cut, scraped, or otherwise removed. This process is called corner cleaning, and is generally accomplished by a separate piece of manufacturing equipment called a corner cleaner.
At this point the sash frame is now ready for glazing. Glazing is typically accomplished by one of two processes. The first readily used process is when an adhesive strip called a glazing tape is attached to a structure on the profile called the glazing leg. Next, an IG unit is adhered to the other side of the glazing tape, and glazing stops are then placed over the IG unit in order to hold the exterior of the IG unit. This process has advantages, in that the equipment and technology to accomplish this is skewed toward the glazing strip manufacturer, and the window manufacturer can form the window with less equipment and capital outlays. However, the drawbacks to this method lie in the increased cost of and limited materials that can be formed into glazing tapes.
The alternative method of glazing is by a process called back-bedding sealing. In this method, a sash frame is placed horizontally on an X-Y back-bedding machine that will lay down a continuous bead of fluid back bedding sealant along the glazing leg. The IG unit is then adhered to the back bedding, and glazing stops are attached. In this method, the back bedding material creates a seal between IG unit and the sash frame. Although additional equipment is required, this process allows the use of a variety of materials, including silicone adhesives, that have advantageous price and/or performance characteristics.
In all cases, IG units must necessarily be manufactured separately, and many times are made by separate company. The trend is to move this step in-house to control costs, size, availability, etc. Also, by controlling more directly the IG unit manufacture, both markets, retrofit (custom) and standard sizes (new installation) can be addressed.
The manufacturing of conventional IG units, as utilized in the manufacture of PVC insulating windows, has been thoroughly addressed within the art, and is meant to be incorporated herein. For purposes of identifying structures and for providing a frame of reference for the present invention, this manufacture shall be briefly discussed. First, a spacer bar is formed, generally of a hollow, roll-formed flat metal, into a hollow channel. Generally, a desiccant material is placed within the hollow channel, and some provisions are made for the desiccant to come into fluid communication with or otherwise affect the interior space of the IG unit. The spacer bar is then notched in order to allow it to be formed into a rectangular frame. Due to the nature and geometry of this frame, the IG unit at this point has very little structural rigidity. At this point a sealant is applied to the outer three sides of the spacer bar in order to bond a pair of glass panes to either opposite side of the spacer bar. Generally in use for this sealant is a polyurethane or polysulfide sealant, due to their combination of strength and moisture barrier characteristics. After application of the glass panes and curing of the sealant, the IG unit finally has structural integrity. The current state of the art is represented by U.S. Pat. No. 5,313,761, issued in the name of Leopold, in which hot melt butyl is directly applied to a spacer element that incorporates a folding corner key. Such a method is embodied in a very difficult and clumsy manufacturing process that incorporates a number of inherent manufacturing problems, one of which is the sealant must set under high heat and pressure, and then set for 1-2 days before curing completely.
A number of other problems exist with the current state of the art in IG unit performance. The use of polyurethane or polysulfide sealants, because of their non-pliable nature when cured, can cause stress fractures of the glass after periods of thermal cycling that cause expansion and contraction of the elements. This leads to fog or moisture intrusion into the interior air space. The use of polyisobutelene sealants have been attempted due to their excellent moisture barrier properties. However, poor structural integrity results. And, although silicone is a strong sealant material, it is porous to moisture intrusion and cannot be used by itself, and must be used as part of a double seal unit (dual seal).
Other recent issues have arisen that have yet to be addressed by the art, and can be characterized by a standard called the "warm edge test". The warm edge test is a thermal conductivity test that rates the insulating properties the IG unit, and is a method of quantifying the insulating capacity of an assembled insulating window, and not just of the component parts. The driving force for this characterization is governmental regulations that require structures have to have certain outside thermal envelope characteristics. However, because of the metal spacer necessary and the inevitable increase in thermal conductance caused by such a structure, conventional IG units perform poorly in this regard. This is mainly due to the fact that conventional IG units were designed to provide insulating properties along the viewable glass area and not increase insulating properties along the perimeter sash and frame areas.
The current state of the art for this technology is also represented by U.S. Pat. No. 5,313,761, issued in the name of Leopold, in which "U" shaped spacers without corner keys are used such that conduits for conductive heat transfer is cut in half. Also, the elimination of corner keys eliminates a natural leak point in the system.
Consequently, a need has therefore been felt for an improved but less complex mechanism that provides a thermally sealed and structurally sealed air pocket formed on two sides by a glass panel for use in otherwise conventional functioning windows.